In one method of manufacturing electrical terminals, the terminals are stamped and formed from metal strip and are attached to a carrier strip. The carrier strip is useful for strip feeding the terminals through successive manufacturing operations. One of the necessary manufacturing operations involves plating, i.e., electroplating the electrical contact surfaces of the strip fed terminals with a contact metal, usually noble metals or noble metal alloys. These metals are characterized by good electrical conductivity and little or no formation of oxides that reduce the conductivity. Therefore, these metals, when applied as plating will enhance conductivity of the terminals. The high cost of the metals has necessitated precision deposition of these metals on the contact surfaces of the terminals, and not on the remaining surfaces of the terminals.
Plating apparatus, also known as a plating cell, includes an electrical anode, an electrical cathode comprised of the strip fed terminals, and a plating solution, i.e., an electrolyte of metal ions. A strip feeding means feeds the strip to a strip guide. The strip guide guides the terminals through a plating zone while the terminals are being plated. The plating solution is fluidic and is placed in contact with the anode and the terminals. The apparatus operates by passing electrical current from the anode through the plating solution to the cathodic terminals. The metal ions deposit as metal plating on those terminal surfaces in contact with the plating solution.
U.S. Pat. Nos. 4,690,747, 4,384,926, 4,427,498 and 4,555,321, owned by this assignee, disclose plating apparatus in which the interior surfaces of strip fed terminals are plated by supplying plating fluid through nozzles and over associated anode extensions or assemblies that are mounted for reciprocation into and out of the interiors of terminals. In effect, each anode extension, nozzle and terminal is a plating cell, and each apparatus comprises a plurality of plating cells. In the first three patents above, the anode extensions are mounted within their associated nozzles. In the fourth patent above, the anode extensions are mounted separately and apart from the nozzles and enter the terminals from a different direction than that of the plating fluid.
The apparatus disclosed in the four referenced patents are designed to be used with stamped and formed terminals, wherein the contact zone is located on the inside surface of a formed terminal. To selectively plate the contact zone the anode extension must be moved inside the terminal. The anode extensions disclosed and used in the above apparatus are particularly suitable for use with electrical socket terminals having a contact area that extends circumferentially around or along the entire inner surface. In some types of socket terminals, however, the contact area comprises only an angular portion of the inner surface of the terminal. In those instances, it is desirable to have a means for selectively plating only that portion of the inner surface that comprises the contact area.